1. Field of the Invention
The present invention generally relates to dual polarized panel base-station antennae for use in mobile communication systems. More specifically, the invention relates to the structure of dipoles used with dual polarized panel base-station antennae.
2. Description of Related Art
Dipole antennae are common in the communications industry, and conventional structures, including half-wavelength dipoles with xe2x80x9cbow tiexe2x80x9d structures and xe2x80x9cbutterflyxe2x80x9d structures, are described in several books, including Banalis, Constantine A., xe2x80x9cAntenna Theory Analysis and Designxe2x80x9d, Wiley, 1997.
In particular, panel base-station antennae, such as those used in mobile communication systems, rely heavily on dual polarization antennae. In many cases, these antennae are constructed using single linear polarized elements, grouped in such a way that creates dual polarization. In this case, two separate arrays of radiating elements are required to radiate on both polarizations.
Building antenna using this approach is undesirable, however, because creating the dual polarization effect with single linear polarized elements increases the labor cost and the number of parts involved in the antenna""s manufacture, while reducing its overall performance. To overcome this, most dual polarization antennae are made with directly dual polarized elements, either by including a single patch element fed in such a manner as to create a dual polarized structure, or by combining two single linear polarized dipoles into one, thereby making a single, dual polarization element.
Feeding signals to and from these dual polarization structures is usually accomplished by conventional coupling structures such as coaxial cables, microstrip or stripline transmission lines, or slits. The drawback to using these conventional coupling structures with the antennae and dipoles described above is that they increase the number of parts needed to construct the antenna, thereby generating undesired intermodulation distortions.
In addition, manufacturing these panel antennae with dipoles that include numerous radiating elements often requires numerous solder joints and screw connections. The total number of parts required in such panel antennae, in addition to the cost of their assembly, makes them unsuitable for mass-production. In addition, solder, screws, and similar types of attachments between parts not only add to the manufacturing time and labor cost, but also generate undesired intermodulation distortions as well.
In addition to avoiding these intermodulation distortions, it is necessary to achieve good port-to-port isolation between the two inputs of the radiating elements in the antenna in order to achieve an efficient communication system. This isolation is the measure of the ratio of power leaving one port and entering the other port. But using the air dielectric transmission lines that are common in conventional coupling structures creates distortions in the signal fed to and from the reflector. In these circumstances, it is prohibitively expensive and difficult to achieve the desired isolation, meaning that the antenna cannot be configured such that one port is used for transmission and the other port for reception.
Finally, in addition to having good port-to-port isolation characteristics and a minimum of intermodulation distortions, it is also important for the dipoles in the antenna array to have a good impedance so that all of the dipoles in the array can be properly matched.
In the view of the above, there is a need in the art for low-cost panel base-station antennae that are easy to assemble, that include a simple arrangement of radiating elements, and require a reduced number of parts and connections. In addition, such antennae must have good port-to-port isolation, good pattern purity, good impedance, and low intermodulation distortion.
The present invention provides a new and useful single or dual polarized antenna for use in mobile communication systems.
A first embodiment of the invention provides a polarized antenna for use in a mobile communication system comprising at least one dipole having a base portion and a plurality of radiating arms extending therefrom, wherein said dipole is formed as a single structure; and a reflector plate to which the base portion is attached, said reflector plate being a ground plane and reflecting polarized radio frequency signals. The dipole may include two sets of arms, including a first set and a second set respectively having a first polarization and a second polarization corresponding to two polarizations of said dipole. Each set of arms preferably includes two pairs of arms arranged in a V-shape and having a vertex portion. A first pair of arms in each set has a first slot at said vertex portion and a second pair of arms has a second slot at said vertex portion for receiving a feed cable, said first slot receiving a cable center conductor and said second slot receiving an insulating jacket. The dipole can also include a cavity for feeding the cable located at the vertex portion of the arms.
The present invention further provides a method of manufacturing a dipole for use in a polarized antenna, comprising forming an entire dipole body as a single piece, including a base portion and a plurality of radiating arms. The dipole body is optimally molded from a conventional material such as plastic, aluminum or the like. In this case, the method of the present invention further comprises plating the molded dipole body with a metallic material that can be soldered.
Accordingly, the invention comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.